Thermography provides an excellent means of screening racehorses for early signs of injury, according to recent research in the USA.
Thermography gives a visual representation of the surface temperature of an object. Recent technological advances have made it a more reliable and convenient imaging technique. Over the past few years thermal imaging cameras have been specifically developed for use in horses. Consequently the use of the technique in horses has become increasingly popular.
Dr Tracy Turner, of the University of Minnesota, describes a two-year study, conducted with colleagues Jennifer Pansch and Julie Wilson. "We wanted to show that the technique could provide meaningful results in a practical situation." says Turner. "We also wanted to find out how well the thermographic findings agreed with the trainers` concerns and with the vets` findings."
During the first year of the study they carried out 225 exams on 45 horses from 7 different trainers. Examinations were performed weekly for ten weeks. They recorded 20 standard images for each horse, which they then analysed to identify abnormalities. Then they compared their findings with the veterinary record of each horse.
The thermographic findings correlated well with the trainers concerns. In 79 of the 225 exams the trainer had specific concerns about the horse. The area of concern coincided with the area highlighted by the thermography in 82% of cases.
Twenty-three of the 45 horses had to be examined by a vet for lameness problems. In all but one case the thermography findings agreed with the vet`s findings. The exception was a case of exertional rhabdomyolysis (tying up).
Nine horses had to stop training because of injury. Three had chip fractures in the knee and one a chip fracture of the fetlock joint. Two had tendinitis. Three horses had soreness affecting more than one bone or joint. In each of these horses, thermography detected the area concerned at least two weeks before the injury was diagnosed.
In the second year of the study they carried out 461 thermal studies on 50 horses from 10 different trainers.
Trainers had specific concerns in 127 of 461 horses. Not only did thermography correctly identify the site of the problem in 95 % of those cases, it did so 2-3 weeks before the trainer became concerned. So, using this technique it was possible to alert the trainer to potential problems.
Twenty of the 50 horses underwent veterinary examination for lameness. Thermography correctly predicted the site of injury in nineteen cases (95%). Obvious changes in thermographic pattern were invariably associated with significant problems (bone chips, stress fractures, tendinitis.)
Nine horses had an abnormal thermal scan of the tendons; eight later developed tendinitis. The thermogram revealed abnormalities in the fetlock of twenty nine horses; fifteen later developed problems at the fetlock. Of fifteen horses with suspicious scans of the knee, ten developed problems. In contrast, forty-one horses had abnormal thermograms of the hock but only nine developed problems in that area.
The number of horses showing abnormal back muscle thermography patterns remained fairly constant throughout the year with the exception of two peaks. These changes coincided both with a recent reworking of the track and coincided with increased complaints of horses not working well.
Turner points out that, as with any other imaging modality, thermography takes experience to interpret. For example, the lame leg may actually appear colder because of transfer of the load to the good leg. He stresses the benefit of repeated exams to detect subtle changes. Its not so much "hot spots" as change in thermal pattern that causes concern.
Several factors influenced the results. The level of work definitely affected the appearance of abnormalities. "Chronic, rested cases are the most difficult to see anything in. I will get them to ride the horse first before I examine it." says Turner. "Maximal exercise was a problem. We found that we couldn`t examine them within two hours. The feet remained hot for 24 hours after a gallop."
"We also learned that liniments and icing did not affect the detection of signs - provided that the horse had both legs treated in the same way."
What about bandaging artifacts? "As long as both legs were bandaged , you could see through the changes" he adds. "If both legs are bandaged we take them off and scan straight away and read through the changes. Over time as we built up the trainers trust in the technique, they removed bandages for 2 hours before - which made the changes much easier to read."
" I use the technique on a daily basis in my clinical work" reports Turner. "Thermography is ten times more sensitive than my hands at detecting changes. I use it at the end of my physical exam - so that I have stressed it as much as I can to accentuate the changes. It doesn`t tell you what is going on. It tells you where to go and look more closely."
He found that trainers readily accepted the technique for what it is, a tool to better manage the horse through the season.
He concludes that "This provides an excellent method for screening racehorses and detecting injuries before they become clinically apparent. So it should be useful in assessing and screening other sport horses during training."
for more details see:
Thermographic assessment of racing Thoroughbreds. TA Turner J Pansch J Wilson. Proc Conference on Equine Sports Medicine and Science 2002 p207